Does Marijuana Cause Schizophrenia?

Last updated on November 4th, 2019

The first time Sascha Altman DuBrul’s parents locked him up in a mental hospital against his will, he was 18 years old and discovered wandering along a New York City subway track in a psychotic mania—after smoking a lot of pot.

“I have a complicated relationship with pot,” explains DuBrul. “There’s a bunch of people out there who when they smoke weed it just makes them happy and laugh and feel stupid. And there are certain people like me who have a predisposition for being, well, sensitive.”

That’s DuBrul’s observation as co-founder of an alternative mental health network called the Icarus Project. But scientists would agree. Evidence of such a predisposition—possibly genetic—is stronger and stronger.


Research shows heavy pot smoking can bring on the frightening delusions and ‘voices’ of psychosis… can also make these experiences more extreme, but only for some.

Research shows heavy pot smoking can bring on the frightening delusions and “voices” of psychosis (usually diagnosed by psychiatrists as schizophrenia) and can also make these experiences more extreme, but only for some.

Teenagers are at extra risk. “Although most young people use cannabis without harm, a vulnerable minority experience harmful outcomes,” pronounced the researchers behind an influential New Zealand study.

It makes sense that young brains, still developing, are more susceptible to drugs, even natural grassy ones. Scientists in Canada have also shown that smoking a lot of pot can cause a precipitous drop in a teenager’s IQ.

The psychosis findings are worrisome:

  • In the New Zealand study, 10 percent of teenagers who started smoking by age 15 developed psychoses by the time they were 26, compared with 3 percent of nonsmokers.
  • A bigger, longer-term project tracked 1,000 teens over 20 years and saw the same odds: Early pot smokers were three times as likely to develop schizophrenia and similar illnesses.
  • A 2011 review of 83 studies found the psychosis age of onset for pot smokers was 2.70 years younger than for non-smokers.

Pot Can Help Too

So then why do some schizophrenics fire up a joint and feel better, not worse? Marijuana is showing promise in lab tests as an anti-psychotic treatment (with the tetrahydrocannabinol or THC removed, leaving cannabidiol or CBD), and internet banter says the rest:

“If in your case being without weed helps you with your psychosis, congrats and good luck,” AnarchiexxxAlex recently told a fellow sufferer online. “However speaking for myself, smoking a joint when my voices get too intense helps tremendously.”

It’s worth noting that other recreational drugs are also hard to match up with the highly subjective symptoms of “madness.” Cocaine and methamphetamines are more likely to contribute to psychosis than to ease it, but plenty of schizophrenics will tell you that coke makes them calmer. (Heroin users are generally at less risk for psychosis than the rest of us.)

What’s remarkable is how little we know about the pot connection, considering its standing as the number one ‘illicit’ drug worldwide and the fact that it’s now legal, after decades of debate, in several U.S. states.

What’s remarkable is how little we know about the pot connection, considering its standing as the number one “illicit” drug worldwide and the fact that it’s now legal, after decades of debate, in several U.S. states. In this country, federal restrictions on marijuana discourage research, but even so.

Until recently, schizophrenia was viewed as a disease of pure brain chemistry. There were just a few known risk factors, all biological: having a mentally ill family member; being a young man; and having a father who was older than average when you were conceived.

Robin Murray at the Institute of Psychiatry at King’s College London has helped shake up the field by recognizing the power of environmental factors such as living in big cities, being a migrant—and smoking pot. He now feels the clearest avenue for improving the situation is getting young people to stop.

“Our findings suggest that cannabis use among psychologically vulnerable adolescents should be strongly discouraged by parents, teachers and health practitioners,” Murray and his colleagues proclaimed. “Policy makers and lawmakers should concentrate on delaying onset of cannabis use.”

A Case of Madness “Unmasked”

Sascha Altman DuBrul is all for warning teenagers about the pot-psychosis risks. He remembers a school counselor trying that with him when he was 16, more from instinct than informed by any medical knowledge. But really, “Why would I listen to her? I remember thinking that all my life I’ve been wanting to feel like this.”

In fact, DuBrul feels the mental wanderings known as psychosis are not always a bad thing.

Whatever causes such episodes, says DuBrul, the answer is not to unquestioningly apply pharmaceutical drugs in an effort to shut them down. Take prescription meds (or smoke pot) if it makes you feel better, he says, but it can also be useful to experience your “madness” unmedicated, ideally in a controlled environment that feels safe, maybe with a doctor or a friend.

What happened to me when I was 18 was that they locked me up and they shot me full of drugs to tame my psychosis—but that didn’t make it go away, it just sort of masked it.-Sascha Altman DuBrul

“What happened to me when I was 18 was that they locked me up and they shot me full of drugs to tame my psychosis—but that didn’t make it go away, it just sort of masked it.” So many years later, “I was smoking a bunch of weed and I was like ‘Oh my God, all those thoughts I was having when I was 18, they were true.’ I got delusional in a way that was actually not helpful at all.”

DuBrul, now 41, aspires to one day be able to enjoy what he calls marijuana’s “universal” thinking without having a breakdown. (And without turning into a vegetable like friends from high school in New York who never cut back.)

He quotes R. D. Laing: “Mystics and schizophrenics find themselves in the same ocean, but the mystics swim whereas the schizophrenics drown.”

According to DuBrul, “The difference between me drowning and being able to just float about my day actually has a lot to do with my own internal ability to self-regulate and the work that I’ve done on being able to be a healthy human being and having dealt with my childhood traumas and so on.”

The Pot Gene

At first glance, stories about pot causing psychosis look instead like “reverse causation”—maybe people are smoking to self-medicate early symptoms of future psychoses. Researchers have done a pretty good job of ruling that out by the kinds of people they enroll in their trials; a 2014 review published in the journal Addiction pronounced this idea “eliminated.”

Now a provocative new study in Australia submits a third theory: that the same genes that predispose some people to schizophrenia may also predispose them to marijuana use.

Robert Power, who led the project, also through the Institute of Psychiatry at King’s College London, told Reuters, “We know that cannabis increases the risk of schizophrenia. Our study certainly does not rule this out, but it suggests that there is likely to be an association in the other direction as well—that a pre-disposition to schizophrenia also increases your likelihood of cannabis use.”

…the same genes that predispose some people to schizophrenia may also predispose them to marijuana use.

This new wave of genetic exploration comes at a time when recreational pot users face a fresh set of health risks, and not just the mental kind. Every year, the synthetic cannabis known as Spice hospitalizes thousands of people, mostly teenagers, with toxic poisoning. Some have kidney damage or even heart attacks—and many experience extreme psychotic episodes.

“If [pot smoking] is ultimately proven as the mechanism responsible for triggering acute and persistent psychosis in some high-risk patients, the advent of synthetic cannabinoids is a particularly worrying development,” according to a recent review of research in a UK journal.

Spice (just one brand of many) is made with tea or a random herbal mix that is sprayed with or soaked in synthetic chemicals, including some that were originally manufactured as fertilizers or cancer treatment. It’s especially attractive—and accessible—to younger teens because it can be picked up inexpensively at a grocery story or gas station, sort of like a candy bar. And it’s still legal in most states.

It’s clear that psychotics should leave these colorful envelopes on the shelf, but so should everyone else. The problem is not just with what it does contain—chemicals never tested on any brains—but what it does not contain: Marijuana’s unique, if still somewhat elusive, medicinal qualities.

The problem is not just with what [spice] does contain—chemicals never tested on any brains—but what it does not contain: Marijuana’s unique, if still somewhat elusive, medicinal qualities.

Smoke Less

Real marijuana is getting riskier too. Even the most basic variety sold in dime bags on street corners or at dispensaries is 15 times stronger than it was 30 years ago, according to the British Lung Association. Several studies draw an especially straight line between strong pot and psychosis.

This means smokers who are at risk for psychosis but won’t quit might be encouraged to smoke less often. Many adult pot users who are schizophrenic find there is a middle point at which the benefits outweigh the risks.

Call it moderation, harm reduction or just plain self-care: “There is a reason almost every mental illness across the board can be combated with marijuana, but the key is to find your correct dose,” BrightEyes advised recently in the Icarus Project’s forums.

On the other hand, it’s a little crazy to take drugs that target your brain without understanding them. (Pot is not the only mysterious one; we don’t know how some prescription mental health drugs work either. Lithium, for instance.)

That leaves marijuana abstinence, a good option for schizophrenics or people at risk, as well as anyone expecting a drug to make their problems go away.

triciafishDE was referring to mentally ill people as a whole when she posted, “Some of us, me included, thought by doing more [pot] we could be happier.?NOT! Until we found out that doing none was even better…and damn it took a long time to figure it out.?There are no short cuts.”

Related: Cannabis Has Medical Value, But Medical Marijuana is a Fraud
Sally Chew is a journalist based in New York City. She was an editor at Time Inc.’s Health.com as well as at Vibe, Out and POZ magazines. She also authored a true crime book and worked as a wire-service reporter overseas.
Photo Source: istock

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